Which process describes a drug entering the circulatory system?

• A. Absorption
• B. Distribution
• C. Pharmacokinetics
• D. Elimination

Answer: (A)

This question tests how a drug first enters the bloodstream after administration. The process by which a drug moves from its site of administration into the circulating blood is absorption. Once absorbed, the drug is carried by the blood to tissues (distribution). Pharmacokinetics covers the overall journey—absorption, distribution, metabolism, and elimination. Elimination is about removing the drug from the body. Note that intravenous administration goes directly into the blood, bypassing absorption, but for most routes, absorption determines how much and how quickly the drug reaches systemic circulation. So the step describing entering the circulatory system is absorption.